Automatic transmissions for automobiles are recognized as wasteful and complex, and yet they remain very popular. The inefficiency of the automatic transmission, with its torque converter, makes it a target for improvement, to reduce fuel consumption and emissions.
Automatic transmissions have also changed speed and torque ratios in several shifts that are noticeable when they occur. A continuously variable transmission that smoothly changes torque and speed ratios is also clearly preferable for an automotive transmission.
Orbital-type drives have long been used in transmissions for speed reduction. For instance: U.S. Pat. No. 1,684,162 (Trumpler), an orbiting bevel gear spider is used to obtain a variable range of speed and power regulation for a drive shaft coupled to a machine tool; U.S. Pat. No. 1,984,830 (Higley) discloses a variable speed drive in which a pair of orbital drive transmissions are used to provide independent connections between a constant speed engine and each of the drive wheels of a heavy-duty, slow-moving, self-propelled vehicle; in U.S. Pat. No. 3,298,251 (Moss), a constant-speed output is obtained from a variable speed input by a transmission incorporating an orbital drive controlled by a variable displacement hydraulic pump/motor arrangement; and U.S. Pat. No. 4,856,370 (Stidworthy) shows a transmission which uses an orbital-type drive and operates as a non-slip automotive clutch.
We have devised as improved orbital drive to provide a continuously variable transmission that smoothly changes torque and speed ratios in an efficient automatic automotive transmission. It uses a direct drive for high gear, has no torque converter, and is more efficient than the automatic transmissions that have reached the marketplace. It also continuously varies speed and torque ratios from a low gear up to the direct drive, so that speed and torque ratios are varied smoothly and continuously throughout this range. Our transmission is compact and no more expensive than a conventional automatic transmission, so that it achieves these advantages without costing more, taking up more space, or suffering other disadvantages.